The present invention relates to a new and improved construction of an open-end friction spinning device for producing a yarn or the like by friction spinning and also is directed to a new and improved method for producing a friction spinning means or element.
Generally speaking, the open-end friction spinning device of the present development is of the type comprising two friction spinning means or elements movable relative to each other and together or coactingly forming a convergent region or zone. At least one of these two friction spinning means or elements is provided with a coating or layer forming a friction surface and with holes or perforations for passage of an airstream or airflow therethrough, the hole cross-section or cross-sectional area being smaller than 0.283 mm.sup.2. There is also provided a fiber feed or transport duct extending between a sliver opening roller or roll and the at least one perforated friction spinning means or element for the pneumatic transport of fibers to the friction surface of the at least one perforated friction spinning means or element. A yarn formation position or location is present on the friction surface in the convergent region or zone between the friction spinning means or elements. Moreover, a yarn withdrawal apparatus or device serves for withdrawing the spun yarn from the yarn formation position or location.
As already indicated previously, the present invention also relates to a new and improved method for producing a friction spinning means or element for the above-mentioned friction spinning device, in which the friction spinning means or element is perforated for throughflow of air and a coating or layer is applied to form the friction surface.
From the German Published Patent No. 3,114,093 which is cognate with U.S. Pat. No. 4,372,109, there is known in this technology a friction spinning device of the previously mentioned type which has a friction spinning drum provided with throughpassing cylindrical holes and a coating on its outer surface. To avoid the existence of too large a resistance to airflow through the holes or perforations, on the one hand, and undesirable passage of fibers or fiber parts through the holes or perforations, on the other hand, the holes or perforations have a diameter of 0.6 mm, which can be increased to 0.75 mm but must be at least 0.5 mm. The holes or perforations are bored mechanically in cylindrical form; this can be effected with a normal borer. It is recognized that a smaller hole diameter would be advantageous for better protection against undesirable penetration of fibers.
It is, however, equally known that boring of very small holes or perforations, where the number of holes or perforations normally provided for the friction spinning means or element is greater than 20,000, leads to problems in manufacture which cause correspondingly high fabrication costs. In order to obtain a surface at the perforated friction spinning means or elements which possesses the desired spinning characteristics or properties and a favorable coefficient of friction with regard to the fibers, the friction spinning means or element is coated, the coating thickness lying in the range of 0.025 to 0.05 mm. The coating may penetrate into the holes or perforations but excessive narrowing or constriction of the holes or perforations is however avoided. Perforated rollers or friction spinning drums with holes or perforations and a coating are also known, for example, from German Published Patent No. 2,943,063 or the corresponding U.S. Pat. No. 4,315,398.